SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e7ddb893cd329a154c01a4e63621d7f8d4feec00ce20171002a8389d652706dd' 
  AND token = 'rnuVS3tgLP2BsCjbg8hFUK+1stqOJvqAcY7R/fCgmFo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}