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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dcfe0a646b440501a7437aaa1d059486d1bcdd96f77f448cb41968e2c651af8c' 
  AND token = '5ZhGS6ogRgWAhwaYb+8KhimNnWDq8NRIlo5LdtGoRGk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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