SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a51cada45dc1c41b3f202400cde45f250170afe7511b057c3b0e705c55a947c2' 
  AND token = 'Pdp3z4t9h3Wsw1+LC01AwYSopZE6DyaHNunILUNIAlM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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