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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51bdeddd08e2f299096ecff21ae63ca8f18dc71a3f4166bc746fa6fe27b7e9a' 
  AND token = 'ERpwkxeDkW30xUmIjQUGdGT0soDzNkWAfeCqm7APjCk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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