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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b942da76a1518df49ca1b86255ccfca2e9006e610a2bd5cfd319e4c3434f88ef' 
  AND token = 'oJIHZjkIfM2IaZtCmZZ5RVrIRT+Up6Qo6KSlHuD+T/c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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