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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '449617396b104ba5e92e13f73ce8600489f9f1d3d552dc8a2437aaafb269fde4' 
  AND token = 'cfA+JRakP1uD7ecTSREsZ7cqVt247SPpNS5S0uUlJlA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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