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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '815f56ad808b183ec45d922891cf8bb952d4516f7a884c411ec7ebb868f7d545' 
  AND token = 'kuQnr3AF+cORkRvDcuXFM6G15yE0DDo0BdEHg+DPjuo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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