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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7eea7c6fad6b4f2bf673e13d736b61a731bdc26e0a8cc7014dd9b9daba2ee376' 
  AND token = 'ND3zwFtj85j2MKgWhCsuF1DemjeDcY23sQUfKvBqYdQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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