SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b142fc00db10716afc55f84844a8463d99488cdb843d137cac400b941159ad83' 
  AND token = 'dHs2tmFbjK3ARJ3amu3M2OJCZqYTcVZgrUnt1e+Phuc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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