SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6da69c64b2baf29de67149b7aa2a42d002d979cc7c18d4ec77665d5d86f3154a' 
  AND token = 'RCxhktw8RPbgPFxz5b/VJzGqH/sAGxIvUy4Ly0YpnDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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