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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8991248aed24ce3fab2cbb7a95d82830c8e2e1296392c2ea692c0da17db14901' 
  AND token = '0Kj7Pr6b6+Kc/PkmS2Sq0SNWMUWPo4379OehvmxENB8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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