SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78f090772224e131f7983812d658c06c3eed9d353a1fd8effa013dddf67c6942' 
  AND token = 'EJwYVh1oZIKXVBY1fjSkHfVHcph5e+jjQlQDLLCDaRU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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