SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e944f498da09966a02c16adc70b44f8016c263d9bdd5037aa0371d786087f4f2' 
  AND token = 'EMsI90KcpRLnb+ylLNVcKL2hnPcy3lQLPjmxvTOC4/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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