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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'f89d3662fad5948326f47f6789602cdaacf9116809b4f7da756a60ea43996554' 
  AND token = 'jd5xrwvS7mj0cr+hro8ZezPJxaE2wUN606dtFMyUq34=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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