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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9c68fcfee9b7bfb76c4959965fe07e2a1eb8719e9e0d0e797dfa668ae628bb39' 
  AND token = 'HDJCLXd1eiBouUv44mib3HiY1/T7ZQrrlOcUHEoPNRo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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