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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21b7aa963b1fa136efc4228ee977b11e61ea5f2e8e77b1dfe067a9835d517b6' 
  AND token = '+Sh7MGdn2vXY+RGPhQ/Dvwt1voQDVOQyqjI6SYyaVtI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00061

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}