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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b2881cda1bb352580c6bd24c8e44fa5bab5ecadda55b7b6f8d6ca44636930f5a' 
  AND token = 'kSEpBQOtCv8b6pHCc/JA2yBqUUFSqN55Ba/IWQzHvVE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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