SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a3fa4147d1e752c5a3b73983d4cedc2484afcfa1b01caf20020c88769c9074' 
  AND token = '2YXn5WhgnwU0tbHpp8GUbIHNcvmVy1928SG96YJGCOY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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