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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '33803e9bb1995d0bf7a94e29c1d35bd09691614ada58b64ddb76ac1025284295' 
  AND token = 'I7SzNfuDK56p/ZnqPHfjIWHtWCKy2fDVci8J7QAdpFA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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