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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51aa15cd60db6d7f30d49d9524f293ccc428dd5e803629e8575484544ff1486c' 
  AND token = '1oSK80UPoUqHRUKIJ5SHSOoI65E00cS0AzXxPBaSshA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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