SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b903517b97df8af9e92eed9775aa7dd285d22856381db0266a5c24059f19c55d' 
  AND token = '3lR37hM2gBJTEABoGMRgqaRzETC3fwsTSZBAGtuue78=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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