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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a4ad05557add0eb6746686c57aa7aa8d35e758c8519135bf1b3d65ac4f4ba05' 
  AND token = 'tDG1ES2hkN9r2mEEMEOu7LeB+AOcWuNRRCeVMVluKCQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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