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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ac03c79348d71a42e8ce21367e92aa9f256799414a06c2c07954a2a52286fb3c' 
  AND token = 'kFWaUhydx0e7AwrDQtBsFzVm1pnB75cn1gDm/XUywI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}