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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '42f5f5cee621f51bff0f4c1524c9b5e3c98ab34940d0590fa219d1216c07923d' 
  AND token = '+214LVUeaSqqP2oBHSBpxYckwceR2Wzig9afVPixBG4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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