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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c6c8765bc95bf4e532fcaf3cf2ad7a73d699b8eb9711e1bf50e54526fde18e0a' 
  AND token = 'uf8OHeTUlq5ocwVSihJ4RAPDxGyXHmcX7J1TPiD/QBI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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