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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b308875515e44cd7e17d9b556a4f7caa5b5121e6056598a1b29bcc8a10b58bd5' 
  AND token = 'Y704eSFsiZ5ovvrLQ2IYSxfOr6+d7QGpVzkIR8rS8Eg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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