SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'abe5976606ef521fb0678da1f2ab48daf9a7d8e337878c379981e4a4932a0d46' 
  AND token = 'viUt+vVSynEMpvAFke0fp7/iCUL4BDDc8MpfCPMeHJQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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