SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e9190c294931200f9e803c8a55be5444150a1c8d19211148b2a513466fa84828' 
  AND token = 'SSzaqHPkl2FYzmRj1QKChj9nZG+iInlSWQic/mnPsww=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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