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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b5adf4fe5525f8f43bc33273bd4d571b3e678a0272f67f74297e1a3a7d8987c5' 
  AND token = 'zJO2kJv+fdX52WtQ6B2qnK3rrHE7FsfoHuL5Uf98Ozg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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