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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b1f1261fa12a64ee65b5590d041e9a2c394beb547cb93be206e39fa5b44c21c1' 
  AND token = 'R8dYPkWEkWQQWRRxe+ehKPGZZjo6ZhJtJNbBggIdrAY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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