SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '0504a97400126bfa7c353991a0135e371402ff237b980a5186b593a6458775e8' 
  AND token = 'Bc1JVQsgRfhbC2LdbP4ttUPFSFGrBuP6Pm/YYH2tKd0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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