SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5d703dd450a8346e1c40af6527426465050ef1ffcf4d05d853859facdcd35d0' 
  AND token = 'GC/Iq/paFz3R7dVFfR4NY0dbub11UsREGWdLw+QvIO4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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